Drill bit



May 31, 1960 S. S. TANNEHILL DRILQBIT Filed March 14, 1955 Ilm-3,

ac 7 n., 2x 2 5 j j F f E! 0 1,/ /q 9 a l 2f /l li 5 y j M /J 3 5 M j a |V 3 9 j f III 0 7 11| il 1113, 3 Il ills] 1 2 1` o. 9 3 1/ 4 2 2 a -lr/ j 3 y s R. J m N m f VM M m. f s M4 M United States Patent O DRILL BIT Selman S. Tannehill, Lynwood, Calif. Diamond Drilling Co., 2759 E. Willow St., Long Beach 6, Calif.)

Filed Mar. 14, 1955, Ser. No. 493,878

2 Claims. (Cl. Z55-300) This invention relates to the art of drilling wells and is particularly directed to improvements in apparatus for drilling deep oil and gas wells.

In present day oil well completion practice, casing may be set at lany desired level. For example, ten thousand feet. The drill string may be inserted through the interior of the casing to drill out the cement plug at the bottom and to drill additional ,open hole below the bottom of the casing into the oil sands. Fifteen hundred feet, for example, of such open -hole may be required. It is highly desirable to drill as large a hole as practicable below the casing but under present completion practice the maximum size hole which may be drilled below the casing is limited by the maximum size bit which may be passed through the casing. In some locations it is relatively much more diliicult to drill the fteen hundred feet of small diameter open hole than to drill the ten thousand feet of large diameter hole to receive the casing.

It is the principal object of my invention to provide apparatus which may be inserted through casing and which will drill a relatively large hole below the casing.

Another object is to provide a novel form of mounting for the bit which will permit the device to drill a larger hole than the nominal size of the bit.

A more particular object ,is to provide a ball and socket mounting for acone roller bit which enables the bit body tormove universally in every direction with respect to the axis of the drill string.

Other and more detailed objects yand advantages will appear hereinafter.

In the drawings:

Figure l is a diagrammatic view showing a well casing and illustrating the operation of drilling below the lower end of the casing.

Figure 2 is a sectional elevation showing a preferred embodiment of my invention, and taken substantially on the lines 2 2 as shown in Figure 3.

Figure 3 is a transverse sectional View taken substantially on the lines 3-3 as shown in Figure 2.

Figure 4 is a diagrammatic plan view showing the path of travel of certain elements on the bit.

Referring to the drawings:

The casing generally designated extends into the well bore 11 and the lower end is sealed with respect to the formation by the annular cement body 12. A rotary drill string 13 of conventional form is inserted into. the casing at the surface. This drill string carries the bit assembly 14 at its lower end. The bit lassembly 14 includes a hollow shank 15 provided with an upwardly extending threaded pin 16. 'Ilhe threaded pin is received within a cooperating threaded socket provided on the lower end of the drill string. The shank 15 is provided with a recess 17 having a substantially spherical surface 18.

A bit body 19 is formed with a ball element 20 on its upper end and the outer surface of this ball element is received in surface contact with the recess 17 in the 2,938,710 n Patented May 31g, 1960 shank 15. A pair of semi-circular split bushings 21 extend into the cylindrical portion 22 of the socket 17 and serve to maintain the ball element 2t! in contact with the socket :17. A spherical surface 23 is formed on each of the bushings 21 for contact with the ball element 20. The body 19 has a cylindrical shank portion 24 connecting the ball element with the enlarged lower end of the body. This cylindrical neck 24 extends through an up- Wardly converging taper bore 25 provided by the cooperating bushing 21. From this description it will be understood that the bit body free to swing universally in every direction rabout the center of the ball element 20 Yand the extent of this movement is llimited by contact of the cylindrical neck 24 with the conical bore 25. The bushing 21 may be held in place by any convenient means such as, for example, welding 26.

The roller cone elements 27 of the bit assembly are conventional in form and are mounted in the usual manner to rotate with respect to the bit body 19. While I have shownthree roller cones 27 in the drawings, it will be understood that a greater or smaller number can be employed as desired. The roller cones are disposed so that the shaper of the bottom of the hole which they produce is convex at the center ofthe bored hole. An upward facing conical protuberance is formed-at the bottom of the hole. v

. drive portion 29 which is square in cross section and which Means are provided for-transmitting torque from the shank 15 to the body 19 and as shown in the drawings, this means includes a plurality of drive pins 28 xed in the shank 15.V Each of these drive pins 28 includes a projectsinto one of several drive pockets 30 formed in the ball element 20. Each of these drive pockets 30 has parallel walls 31 adapted yfor contact with the driving portion 29 of the pins 28. Since the dimensions of,

the pockets 30 are larger than therdimensions of the drive portions '29 of the pins, the ball element 20l has universal movement within the socket 17 but is caused to rotate as ,a unit with the shank 15. Y

An `passage 32 in the shank 15 is aligned with an axial passage 33V in the body 19 and these passages serve to carry drilling uid to the roller cones 27 and to carrythe 1cuttings'upward within the hole outside 'of the bit assembly.) In'operation, the bitv device 14 is attached to the lower end of the drill string 13 and is lowered through the interior of the casing 10. Turning movement of the drill string causes the bit assembly to drill out the cement plug at the bottom of the casing and to continue on into the formation. The ball and socket mounting for the bit body allows the bit to swing laterally to the extent shown by the dot and dash lines 34 of Figure 2. Actual tests show that the hole produced by the bit is larger than the nominal diameter of the bit. The bit swings crosswise from side to side from about the center of the ball 20, While the bit is rotated by the drill string. The shank 15 turns on the Iaxis of the drill string but the bit body 19 is free to swing universally within the Iangular limits imposed by the taper bore 25 of the bushing 21. The extent of lateral movement permitted by the surface 25 and the lengt-h of the assembly from the imaginary center of the ball 20 to the lower end of the bit are such that the outermost cutting edge of the bit cones cannot pass beyond Ithe' center of the hole. The lateral swinging action of the body 19 while the body and shank 15 are rotating is caused by the action of the bit cones 27. Should one cone be loaded heavier than the others, the resulting ofi-center force on the bit causes it to swing laterally to spread the load on the other cones, but such swinging movement in turn loads another cone beyond its proportionate share with the result that lateral swinging continues to cause precessional Iorbital movement of the cones as shown in Figure 4.

One of the advantageous features of my invention is that a relatively large threaded connection 16 may be.

used as compared to the diameter of the lower portion of the bit ,body 19. It is well known that the lowermost` is; 'subjected to the most severe stressesY in service;Y The relatively' large ysize vpin connection is therefore, highly desirable. Another beneficial feature of my invention is that-'relatively large cone elements 27 may be employed compared V'to the Vlateral dimensions of the, bit body. Furthermore the lateral swinging 4action of the bit body asvit rotates under power producesa novel cutting action ink that therrollerrcones 27 do not'merely revolvein circlesrbut on the other handfollow the generalj pattern Yshown in Figure v4. Each roller cone in turn Vcutsto the full outside diameter-aud then to a lesser diameter dur# ing the* operation of the bit. In the diagrammaticillustration of Figure 4, the Ifull lines indicate thek pathY of rone of the bit cones, the dash lines indicatejthe path of another and the dot and dash lines indicatethe pathof a t'hird. The outer circle in Figure 4 represents'theY outshank rotates said body, said means including drive pins fixed von the shank land extending into Ysaid ball element, the ball element having recesses therein of larger diam` eter than the drive pins to receive the drive pins and permit universal movement of the bit body in the shank, a bushing iixedly mounted on the llower end of the shank, said bushing including a partial. spherical seat engaging the ball element, roller cone Yelements mounted on the lower end of the body anddispsed to produce a drill hole having a central raised protuberance, and means on the shank engageableby the'y bit body actingl tovrlimit the extent of universal' swivelling movement about the vvert-ical center Yof. tlie'l ball Veleirlentto 'prevent the outer socket formedin the lower end thereof, a bit body, a

side diameter of the drilled hole.Y The unusual pathnof Y travel of these bit cones is derived from'the universal swivelling mount Vprovided by the ball andsocket joint,

togetherv with the mounting of the bit 'cones ,to produce' a' high center drill hole.

I have found that it is practicable to permit sutlcient Y lateral movement of the bit body A19Y to enable thel cones toproduce'vfa drill hole diameter of substantially larger diameter than `.the hole which is drilled when the bit center line of 4the bit body is in vertical alignment with Y the vertical'center line of the `shankr15. This position is shown in solid lines in Fig. 2 of the drawing.

Y HavingA :Eully described my invention it is to be underf, element tting Within the socket for limited Vuniversal Vswivelling movement therein, torque 'transmitting' means extending from the shank into the body wherebysaid body'19 is in vertical position, that is, when the vertical ball element at the upperv end of saidV bitV body, Ysaid ball element fitting within the socket for limited universal swivelling movement therein, .torqueV transmitting means extending Yfrom the shank'fint'o the Vbodywhereby said shank rotates said body, said means including drive pins fixed on the shank and extending into said ballelement, thejballelernent having recesses',thereinV .o f klarger dialneterthan the drive pins to'rec'eive the-driveV pins and permit universal movement of the bitbo'dy inthe shank, a bushing lixedly mounted onV theA lower end of the shank, sia-id Ybushing including a .partial spherical seat engaging the bal-l element, roller' cone elements mounted on the lower end of the body and disposed to produce a drill hole having a centralraised protuberance, and means on the shank engageable by the bit body .actingV to limit the extent of universal swivelling movement about the vertical center of therball element to prevent the outer edges of the bit elements `from moving past the central vertical axis of the shank, said last named means on the'shank including an outwardly tapered bore in the bushing, said body extending through the outwardly tapered bore.

f References Cited'in the'le of patent Y y UNITED STATES PATENTS Tann-: 

